Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758067Ab3EGSgn (ORCPT ); Tue, 7 May 2013 14:36:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3325 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751602Ab3EGSgl (ORCPT ); Tue, 7 May 2013 14:36:41 -0400 Date: Tue, 7 May 2013 14:00:09 -0400 From: Dave Jones To: Peter Hurley Cc: Greg Kroah-Hartman , Linux Kernel , Jiri Slaby Subject: Re: 3.9+ tty lockdep trace. Message-ID: <20130507180009.GA16771@redhat.com> Mail-Followup-To: Dave Jones , Peter Hurley , Greg Kroah-Hartman , Linux Kernel , Jiri Slaby References: <20130501154723.GB11841@redhat.com> <20130506180020.GB1309@redhat.com> <20130506184059.GA22897@kroah.com> <51890C31.3000203@hurleysoftware.com> <20130507150423.GA13062@redhat.com> <51893B68.1010907@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51893B68.1010907@hurleysoftware.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2074 Lines: 45 On Tue, May 07, 2013 at 01:35:36PM -0400, Peter Hurley wrote: > On 05/07/2013 11:04 AM, Dave Jones wrote: > > On Tue, May 07, 2013 at 10:14:09AM -0400, Peter Hurley wrote: > > > > > >> Just hit this again, by switching tty's during bootup. > > > >> The previous time was switching from X to console iirc, so that seems to be > > > >> the key to triggering this. > > > > > > > > Sorry for not getting back to this sooner, merge window fun... > > > > > > > > Anyway, Peter, could this be something that your ldisc patches are > > > > triggering? > > > > > > Yes, although early analysis also suggests the lockdep splat is possible > > > regardless, just much less likely. > > > > > > I looked at this over the weekend, but I wasn't able to determine (in > > > the limited time I had available) if the splat was valid; ie., if the > > > cpu states could actually be concurrent and result in deadlock. > > > > > > I need to study the VT_DISALLOCATE ioctl in more detail which I plan > > > to do this week. > > > > I don't know if it proves/disproves anything, but shortly before the dump > > gets printed, everything is kind of locked up. I can switch tty's, but > > the gettys on them are dead to the world until after the dump. > > > > ISTR a pause for a while when I hit this switching from X too. > > It would help to know the steps to reproduce. For example, you mention > unresponsive gettys but the VT_DISALLOCATE ioctl doesn't work (and isn't > designed to) on open ttys. Hmm, dunno. I booted up, and tried to log in on tty1 (no X on that box), and after I entered my password everything just hung for a while. I flipped to tty2 to try and log in as root, but after changing tty, I just got a blinking cursor. 10 seconds or so later, lockdep spew. Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/